Conventionally, in order to maintain a flowable substance free of contaminants, preservatives have been added to the flowable substance. However, the use of preservatives tends to be detrimental to many users and can often limit the effectiveness of the flowable substance. Over time and through repeated use they are even likely to be harmful, as they are absorbed through one or more of a patient's or user's mucous membranes, orifices, skin, etc., particularly when the flowable substance is a pharmaceutical such as, for example, an eye care solution, an intranasal drug or moisturizer, a cosmetic treatment or a skin treatment product. Nonetheless, this type of product is most often formulated with preservatives. Of course the flowable substance may also be, for example, a foodstuff, beverage, nutraceutical or cosmeceutical product, all of which are generally formulated with preservatives. As is becoming more and more well known, such preservatives can have a variety of long standing harmful effects. For example, the well known preservative benzylkonium chloride, or BAK, which has been used in a wide variety of pharmaceutical preparations since the 1930s and 1940s, and is currently used in numerous glaucoma therapeutics, turns out to exhibit “very significant toxicity and the production of inflammatory mediators.” Fechtner, Robert D., Asbell, Penny A. and Kahook, Malik Y., Ocular Surface Disease in the Presence of Glaucoma, Supplement to Glaucoma Today and Advanced Ocular Care, February March 2011 at 6. In fact, “preservatives are the number one-cause of worsening dry eye disease and OSD as well as of perpetuating patients' pain syndrome.” Id. at 5. Similarly, in describing BAK as the most common preservative in ophthalmic preparations, Dr. Herbert L. Gould noted “[i]t has well been demonstrated that this chemical, while moderately bactericidal, is highly toxic to the cornea and conjunctiva as well as to nasal mucous membrane.” Gould, Herbert L., MD, Solving the Preservative Paradox, Opthalmology Management, August 2006, 4752, at 47, “When solutions containing this preservative are frequently applied, serious tissue damage has been reported.” Id. The article goes on to describe how long term use of eye drops with BAK has been shown to cause, inter alia, cataracts and maculopathy, damage to epithelial cells, inflammation and damage to the cornea, Id. at 47-52. What is yet to be studied is the cumulative effect on middle age and elderly persons of using multiple preparations, each containing various and sundry preservatives, over years and even decades. It may very well be that the cumulative negative effects of the preservatives, on balance, outweighs any beneficial effect of the pharmaceuticals and other flowable substances being used and ingested.
Another consideration in the dispensing or delivery of a flowable substance is the ability of a delivery system to deliver a selected amount of a flowable substance to its intended destination without causing any damage to the user, such as, for example, when applying an eye care solution directly into the eye without introducing any contamination.
In the past, flexible membranes have been used to control the flow of such a flowable substance to a valve assembly outlet while preventing any backflow to the source of the flowable substance. However, such valves (such as, for example, the valve type described in U.S. Pat. No. RE 34,243) involve the use of O-rings in conjunction with a uniformly thick flexible membrane to effect a seal. This is cumbersome to manufacture and assemble. Other valve assemblies require squeezing a reservoir of flowable substance in order to dispense the flowable substance. Such squeezing can be difficult for the very young—or the very old—as well as for physically challenged or disabled individuals.
Therefore, an effectively designed and easy to operate valve assembly and easily actuated metering delivery system for delivering or dispensing pure or sterile, preservative-free flowable substances is highly desirable. Further, such a delivery system should be capable of being manufactured economically, by (i) reducing the costs of component parts and (ii) allowing the use of high speed automated production, which itself is also required by many regulators.
Thus, what is needed in the art is a delivery system and method for the metered dispensing and maintenance of preservative-free flowable substances in a multi-dose format, that at the same time can prevent contamination in the delivery or dispensing system, that can solve the above-described problems of the prior art.